Detecting Infection With E-nose

It is well known that hospital infections caused by MRSA (methicillin-resistant Staphylococcus aureus) antibiotic-resistant bacteria can be tragic for the patient. New Scientist reports on a device that promises to improve identification of these superbugs.

Culture tests routinely used to identify MRSA take two or three days to complete. This hampers attempts to manage outbreaks as infected patients remain untreated and at risk of infecting others.
DNA-based tests are being trialled that promise to reduce test times to 2 hours, but now UK-based researchers have come up with a test using an electronic sniffer that could cut the time further, to just 15 minutes.
Engineers at the University of Warwick and doctors at the Heart of England Hospital, Birmingham, say the electronic nose can recognise the unique cocktail of volatile organic compounds that S. aureus strains excrete.
E-noses analyse gas samples by passing the gas over an array of electrodes coated with different conducting polymers. Each electrode reacts to particular substances by changing its electrical resistance in a characteristic way. Combining the signals from all the electrodes gives a “smell-print” of the chemicals in the mixture that neural network software built into the e-nose can learn to recognise.
David Morgan, a surgeon at the hospital, says the idea of sniffing out superbugs came to him one day in the operating theatre. “I was operating on neck abscesses on two different patients and noticed their infections had slightly different smells, so I wondered if a machine could work out what the bacterial infections were from the smell alone.”
The e-nose system cannot yet distinguish the methicillin-resistant superbug from the methicillin-susceptible strain. If it cannot be trained to do so, Morgan suggests the e-nose be used as a quick screening system to prioritise which patients or healthcare workers are given the 2-hour DNA-based test, which can tell the difference.